Contribution of sulfonyl–aromatic and sulfonic acid–aromatic interactions in novel sulfonyl/sulfonic acid-embedded reversed phase materials

Two novel sulfonyl-embedded reversed phase materials with sulfonic acid moieties (SOX-RP) were prepared by a simple oxidation of two silica-based sulfur-embedded RP-phases (S-RP). The chromatographic behavior of the resultant sulfonyl/sulfonic acid-embedded phase C3-SO2-C18/SO3H and the sulfonyl-embedded phase C3-SO2-C14 e.c. (silanol endcapped) was extensively elucidated with a number of well-established as well as self-assembled column tests. These SOX-RP phases were also compared with their corresponding S-RP phases as well as with two commercial carbonyl-containing RP phases (CO-RP) with amide- and urea-embedding. The SOX-RP phases were found to exhibit exceptionally high planar recognition ability for polyaromatic analytes at comparable retention times to the investigated CO-RP phases and highly reduced retention compared to the parent, non-oxidized S-RP-materials. The results of this study suggest that the selectivity enhancement observed with the S-oxidized phases is due to sulfonyl–π and sulfonic acid–π interactions. Furthermore these novel SOX-RP phases proved to be fully applicable under 100% aqueous mobile-phase conditions making them a useful alternative to conventional RP as well as polar-embedded CO-RP phases.